If you draw an uppercase 'E', you should have the same amount
of space over and below the 'E' if the text is correctly centered
vertically.

But in the current gnustep-gui implementation, the 'E' is too low.
There is more space over the 'E' than below - the text is not
centered vertically correctly.

This is a regression, because eg, in Renaissance gnustep
screenshots from 2002 the text is perfectly centered
vertically inside buttons [but then, we didn't have proper
anti-aliased fonts at the time ;-)].